1. Field of the Invention
This invention relates to construction materials and, more particularly, to an improved type of interlocking mortarless structural concrete building block system.
2. Description of the Related Art
The origin of the common concrete block in use today was meant as a component to compliment the prior primary masonry building unit, the common clay fired brick. The larger size of the concrete block created greater installation economy over brick and eventually dominated the building industry.
Concrete blocks are also referred to as concrete masonry units or cmus. The majority of these blocks are produced by hydraulic press machinery and vibrated under pressure in steel molds. The final product is usually heavy and rough in texture. While most concrete block usually have vertical cellular cores, the majority of these cores are non-communicative horizontally. The open cells within a wall of this type are filled with additional flowable concrete known as grout. Depending on the type of block system or engineering requirements, there is great variety on the location of grouted cells in any solid masonry wall. Concrete block are intended to emulate the functionality and strength of a poured-in-place reinforced concrete wall, which has greater strength to thickness ratio.
As most concrete block applications are attempts to create a solid uniform concrete mass, such as poured-in-place concrete, the relative performance of a cmu structure should match the inherent strength potential of a monolithically poured concrete wall. Conventional wisdom makes up for this discrepancy by simply creating thicker cmu walls to overcome their inherent engineering weaknesses over poured-in-place walls.
Concrete block suffers from any number of performance deficiencies, yet still constitute a standard in the concrete building industry. From a production standpoint, the manufacture of these types of blocks is economical; however, their actual performance is marginal. While there have been many attempts to overcome inherent deficiencies, there still exist a number of problems that create disadvantages:
a) Common to most concrete blocks is a size and weight that makes placement cumbersome. The functional elements are limited by a dense concrete shell, which severely restricts communication from core to core and which adds unnecessary weight while serving marginal functionality.
b) The majority of these cells are usually vertical, although some cells have provision for horizontal channels. There is little horizontal cohesion in a wall of this nature except what is achieved by lateral reinforcement bars.
c) Between each block is laid a horizontal bed of mortar, the bed joint, and a vertical line of mortar, the head joint. The blocks essentially remain separate, even after their cavities are filled by grouting. The bed and head joints do little for structural integrity, merely adding a heavy mass of mortar to glue the separate cmus. The result is a substantial amount of nonfunctioning mass verses overall intended functionality, or structural deficiency. This is demonstrated by the number of uncommunicated cells that characterize this type of system. Walls of this type have a tendency to fail exactly on joint lines. Mortared joints do little for overall structural integrity as compared with an integral monolithic mass of concrete.
d) Conventional block are labor intensive, somewhat technical, and restrictive to specific labor and strength requirements. Unskilled labor is often deterred from their use due to these reasons. The process is also slow, even for a skilled mason, due to both the size and weight of the blocks and the time consumed in mortaring every joint and aligning and leveling each unit.
e) While attempts have been made in alignment with mortarless systems, either of concrete or plastic cmus, another problem has been creating systems with tolerances too tight to accommodate minor fluctuations that can occur in a foundation or wall layout, and as result, modification of these cmus on site can be laborious, frustrating, and time consuming.
f) Every conventional block must precisely float on a bed of mortar, which requires constant use of leveling devices. This requires additional installation time.
g) Conventional block, due to their limited cellular structure, make the placement of horizontal reinforcement bars or other transit tubes restrictive. To overcome this, many block systems have portions of the block that can be knocked out, but this is another labor step and wasteful of material. These types of block depend solely on reinforcement for horizontal tensile strength, since there is usually little horizontal communication between the blocks for the filling concrete to either pass or reside. Instead are a series of mortar/concrete interfaces with no common singularity or monolithic mass.
h) Many of the plastic systems provide little structural integrity and rely totally on the concrete grout fill for anything structural. These types of systems also require subsequent coatings to seal the plastic from air and moisture penetration.